Device/UE-Oriented Beam Recovery and Maintenance Mechanisms

ABSTRACT

Aspects of this disclosure provide techniques for detecting and recovering from beam-failure events. In some embodiments, motion sensor information generated by motion sensors on a UE is used to detect, predict, and/or recover from a beam failure event that results, or would otherwise result, from movement of the UE. The motion sensor information may be used to adjust a current beam direction used by the UE to transmit or receive a signal, or to determine a recommendation for adjusting a current beam direction of the base station. The motion sensor information may be generated by any sensor that detects a movement of the UE, such as a gyroscope, an accelerometer, a magnetometer, a global positioning system (GPS) sensor, a global navigation satellite system (GNSS) sensor, or any other device that detects a change in position/orientation of the UE.

This application is a continuation of U.S. application Ser. No.15/681,087 filed on Aug. 18, 2017 and entitled “Device/UE-Oriented BeamRecovery and Maintenance Mechanisms” which claims priority to U.S.Provisional Patent Application 62/442,836 filed on Jan. 5, 2017 andentitled “Device/UE-Oriented Beam Recovery and Maintenance Mechanisms”and U.S. Provisional Patent Application 62/453,827 filed on Feb. 2, 2017and entitled “System and Method for Device Oriented Beam RecoveryTriggering,” both of which are incorporated herein by reference as ifreproduced in their entireties.

TECHNICAL FIELD

The present invention relates generally to telecommunications, and inparticular embodiments, for device/UE-oriented beam recovery andmaintenance mechanisms.

BACKGROUND

In Fourth generation (4G) Long Term Evolution (LTE) networks,beamforming is generally only performed by the base station. FifthGeneration (5G) wireless networks will likely use higher carrierfrequencies, such as millimeter Wave (mmW) signals, which tend toexhibit high free-space path loss. To compensate for high path lossrates, 5G wireless networks will likely use beamforming at both the basestation and user equipment (UE). For example, a base station may use atransmit (TX) beam direction to transmit a downlink signal, and the UEmay use a receive (RX) beam direction to receive the downlink signal.Likewise, the UE may use a TX beam direction to transmit an uplinksignal, and the base station may use an RX beam direction to receive theuplink signal. As used herein, the term “beam direction” refers to aradio antenna pattern that is used for directional signal transmissionand/or reception. Notably, due to spatial reciprocity, a beam directionused by a device to transmit a signal will generally offer similarlevels of spatial performance when used by the device to receive asignal. Accordingly, a base station may use the same beam direction totransmit downlink signals and receive uplink signals, and a UE may usethe same beam direction to transmit uplink signals and receive downlinksignals.

SUMMARY

Technical advantages are generally achieved, by embodiments of thisdisclosure which describe device/UE-oriented beam recovery andmaintenance mechanisms.

In accordance with an embodiment, a method for adjusting transmissionand/or reception parameters is provided. In this embodiment, the methodincludes transmitting or receiving an initial signal over an antenna ofa user equipment (UE) to or from a base station, collecting motionsensor information from one or more motion sensors of the UE,determining a transmission or reception (TX/RX) parameter adjustment forthe base station based on the motion sensor information, and sending aUE-initiated recommendation to a base station, the UE-initiatedrecommendation recommending that the base station make the TX/RXparameter adjustment prior to transmitting or receiving a subsequentsignal from to or from the UE. In one example, the one or more motionsensors include a gyroscope, an accelerometer, a magnetometer, a globalnavigation satellite system (GNSS) sensor, or a combination thereof. Inthat example, or another example, determining the TX/RX parameteradjustment comprises classifying a movement of the UE based on themotion sensor information, and determining the TX/RX parameteradjustment based on the classification of the UE movement. Classifyingthe movement of the UE may include classifying the movement as a UEdisplacement or a UE rotation. Optionally, in any one of the precedingexamples, or in another example, the UE-initiated recommendationrecommends that the base station adjust a beam direction used totransmit or receive the initial signal prior to transmitting orreceiving the subsequent signal.

In accordance with another embodiment, another method for adjustingtransmission and/or reception parameters is provided. In thisembodiment, the method includes transmitting or receiving an initialsignal over an antenna of a user equipment (UE) in accordance with abeam direction, collecting motion sensor information from one or moremotion sensors of the UE, adjusting, by the UE, the beam direction usedto receive the initial signal, based at least in part on the motionsensor information, and transmitting or receiving a subsequent signalover the antenna of the UE in accordance with the adjusted beamdirection. In one example, the one or more motion sensors include agyroscope, an accelerometer, an magnetometer, a global navigationsatellite system (GNSS) sensor, or a combination thereof.

In accordance with an embodiment, a method for transmitting a signal isprovided. In this embodiment, the method includes transmitting a firstuplink signal from a UE to a base station The first uplink signalindicates that a UE-initiated beam failure event has occurred. In oneexample, the first uplink signal is transmitted over an uplink randomaccess channel that spans different time-frequency resources than aphysical random access channel (PRACH) used for initial access. In suchan example, wherein the first uplink signal may include a uniquepreamble sequence assigned to the UE by the base station. The uniquepreamble sequence may be one of a plurality of different uniquepreambles assigned to different UEs for signaling UE-initiated beamfailure events over the random access channel, and the plurality ofdifferent unique preambles may be used by the base station to identifywhich UE transmitted a given UE-initiated beam failure event indication.The unique preamble sequence may have been assigned to the UE by thebase station at an earlier time instant. Optionally, in any one of thepreceding examples, or in another example, the first uplink signal istransmitted over an uplink grant-based access channel. Optionally, inany one of the preceding examples, or in another example, thegrant-based access channel is a physical uplink control channel (PUCCH)or a physical uplink shared channel (PUSCH). Optionally, in any one ofthe preceding examples, or in another example.

The method further includes monitoring a plurality of downlink channelsfor downlink reference signals transmitted by the base station, where atleast some of the downlink channels being associated with different beamdirections, and detecting the UE-initiated beam failure event upondetermining that none of the downlink reference signals, having areceived signal quality or power level that exceeds a quality or powerthreshold, have been received over the downlink channels prior toexpiration of a time-out period. In such an example, the quality orpower threshold may correspond to a level required for reliablereception of a downlink reference signal, the downlink channels may beassociated with one or more frequencies, and/or the first uplink signalmay be transmitted over a frequency that is different than the one ormore frequencies associated with the downlink channels. Optionally, inany one of the preceding examples, or in another example, the downlinkchannels include physical downlink control channels (PDCCHs), physicaldownlink shared channel (PDSCHs), or combinations thereof.

Optionally, in any one of the preceding examples, or in another example,the method further includes monitoring one or more downlink channels fora plurality downlink reference signals transmitted by the base station,at least some of the downlink reference signals being associated withdifferent beam directions, and detecting the UE-initiated beam failureevent upon determining that none of the downlink reference signals,having a received signal quality or power level that exceeds a qualityor power threshold, have been received over the one or more downlinkchannels prior to expiration of a time-out period.

Optionally, in any one of the preceding examples, or in another example,the method further includes transmitting uplink reference signals over aplurality of uplink channels, at least some of the uplink channels beingassociated with different beam directions, and detecting theUE-initiated beam failure event upon determining that no acknowledgementmessages associated with the uplink reference signals have been detectedprior to expiration of a time-out period.

Optionally, in any one of the preceding examples, or in another example,the first uplink signal further includes a UE-initiated recommendationfor recovering from the UE-initiated beam failure event. In such anexample, the UE-initiated recommendation may include a recommendationfor changing a beam direction being used by the base station fortransmitting or receiving data to or from the UE. In the same example,the recommendation for changing the beam direction may be indicated byan index in the UE-initiated recommendation. Optionally, in any one ofthe preceding examples, or in another example, the UE-initiatedrecommendation includes a recommendation to initiate a new beammanagement procedure.

Optionally, in any one of the preceding examples, or in another example,the UE-initiated recommendation recommends initiating a handover of theUE from the base station to another base station.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the embodiments disclosed herein,and the advantages thereof, reference is now made to the followingdescriptions taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a diagram of a wireless communications network;

FIGS. 2A-2E are diagrams depicting how different beam managementsolutions may be used to adjust beam directions in a manner thatmitigates beam blockage conditions for different classifications of UEmovement;

FIG. 3 is a diagram of an embodiment network in which Global NavigationSatellite System (GNSS) coordinates of base stations may be used forbeam management or to initiate a handover;

FIG. 4 is a block diagram of an embodiment UE configured to perform beammanagement based on movement sensor information;

FIG. 5 is a flowchart of a method for using motion sensor information toupdate TX/RX parameters of a base station;

FIG. 6 is a flowchart of a method for using motion sensor information toupdate a beam direction of a UE;

FIG. 7 is a flowchart of a method for using GNSS coordinates ofneighboring base stations to initiate a handover of a UE from a servingbase station to a target base station;

FIG. 8 is a flowchart of a method for using motion information of a UEto determine a TX/RX parameter adjustment recommendation for a servingbase station or the UE at a location server;

FIG. 9 is a protocol diagram of a communications sequence for usingmotion information of a UE to determine a TX/RX parameter adjustmentrecommendation for a serving base station or the UE at a locationserver;

FIG. 10 is a flowchart of an embodiment method for detecting aUE-initiated beam failure event according to uplink reference signaltransmissions;

FIG. 11 is a flowchart of an embodiment method for detecting aUE-initiated beam failure event according to downlink reference signaltransmissions;

FIG. 12 is a block diagram of an embodiment processing system forperforming methods described herein; and

FIG. 13 is a block diagram of a transceiver adapted to transmit andreceive signaling over a telecommunications network according to exampleembodiments described herein.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The structure, manufacture and use of embodiments are discussed indetail below. It should be appreciated, however, that this disclosureprovides many applicable inventive concepts that can be embodied in awide variety of specific contexts. The specific embodiments discussedare merely illustrative of specific ways to make and use the invention,and do not limit the scope of the invention.

In addition to using beamforming to both transmit and receive signals,5G wireless networks will likely use finer beam directions than 4G LTEnetworks in order to achieve sufficient antenna gain. Fine beamdirections direct more of the beam's power toward the borescope of theprimary lobe of the antenna pattern than coarse beam directions, therebyenabling fine beam directions to exhibit higher antenna gain than coarsebeam directions when there is a relatively small angular distancebetween the target device and the borescope of the corresponding beamdirection. The terms “fine beam direction” and “coarse beam direction”are relative terms that are used in the detailed description, and shouldnot be construed to limit the scope of the claims. However, this alsorenders fine beam directions more susceptible to beam blockageconditions and/or reductions in quality of service (QoS) than coarsebeam directions as the angular distance between the target device andthe borescope of the corresponding beam direction increases due tomovement of the UE.

Conventional beam management schemes generally rely on beam-scanningtechniques to adjust the beam direction being used to transmit orreceive a data signal in a manner that compensates for UE movementand/or changes in the condition of the air interface. As used herein,the term “current beam direction” refers to a beam direction that isbeing used by a UE to transmit or receive a data signal. Beam-trackingtechniques typically rely communicate reference signals in beamdirections that have boresights which are slightly offset from aboresight of the current beam direction used by the UE and/or basestation. The receive power or quality level of the reference signals arethen compared to the received power or quality level of the data signalto determine whether the current beam direction needs to be adjusted.Beam-tracking techniques may offer relatively good performance when UEsare moving at relatively slow rates of speed and/or the condition of theair interface is relatively static. However, when UEs aremoving/rotating at high rates of speed or the condition of the airinterface is changing rapidly, beam-tracking may be unable to update thebeams quickly enough, and a beam failure event may occur.

Aspects of this disclosure provide techniques for detecting andrecovering from beam-failure events. In some embodiments, motion sensorinformation generated by motion sensors on a UE is used to detect,predict, and/or recover from a beam failure event that results, or wouldotherwise result, from movement of the UE. In one example, motion sensorinformation is used to adjust a current beam direction used by the UE totransmit or receive a signal. In another embodiment, motion sensorinformation is used to determine a recommendation for adjusting acurrent beam direction of the base station, which may then becommunicated to the base station via a UE-initiated recommendation. Themotion sensor information may be generated by any sensor that detects amovement of the UE, such as a gyroscope, an accelerometer, amagnetometer, a global positioning system (GPS) sensor, a globalnavigation satellite system (GNSS) sensor, or any other device thatdetects a change in a position or orientation of the UE. Because motionsensors are generally more sensitive, and responsive, to UE movementthan reference signal measurements alone due to, inter alia, propagationdelay of the air interface, using motion sensor information for beammanagement may reduce the time required to detect and recover from abeam failure event. Although much of this disclosure discusses usingmotion sensor information generated by a motion sensors of a UE toadjust beam directions of the UE and/or base station, it should beappreciated that motion sensor information may be used to adjust anytransmission or reception (TX/RX) parameter of the UE and/or basestation, as well as to trigger a handover from a serving base station toa target base station.

In other embodiments of this disclosure, reference signals arecommunicated over channels associated with different beam directions inorder to detect a UE-initiated beam failure event and/or trigger aUE-initiated beam recovery procedure. In one example, a UE transmitsuplink reference signals over uplink channels associated with differentuplink TX and/or RX beam directions. The UE then determines whether thebase station returns an acknowledgement message associated with one ofthe uplink reference signals prior to expiration of a time-out period.If no acknowledgement messages are received prior to expiration of thetime-out period, then the UE detects a UE-initiated beam failure event,and sends a signal indicating that the UE-initiated beam failure eventhas occurred to the base station. In another example, the base stationcommunicates downlink reference signals over downlink channelsassociated with different uplink TX and/or RX beam directions. The UEmonitors the downlink channels, and if none of the downlink referencesignals are detected prior to expiration of the time-out period, the UEdetects a UE-initiated beam failure event, and sends a signal indicatingthat the UE-initiated beam failure event has occurred to the basestation. The signal indicating that the UE-initiated beam failure eventhas occurred may be communicated over grant-free resources, such as aphysical random access channel (PRACH) used for initial access or arandom access channel that spans different time-frequency resources thanthe PRACH. Alternatively, the signal indicating that the UE-initiatedbeam failure event has occurred may be communicated over a physicaluplink control channel (PUCCH) or a physical uplink shared channel(PUSCH). These and other inventive aspects are discussed in greaterdetail below.

FIG. 1 is a network 100 for communicating data. The network 100comprises a base station no having a coverage area 101, a plurality ofUEs 120, and a backhaul network 130. As shown, the network base stationno establishes uplink (dashed line) and/or downlink (dotted line)connections with the user equipments (UEs) 120, which serve to carrydata from the UEs 120 to the network base station no and vice-versa.Data carried over the uplink/downlink connections may include datacommunicated between the UEs 120, as well as data communicated to/from aremote-end (not shown) by way of the backhaul network 130. As usedherein, the term “base station” refers to any component (or collectionof components) configured to provide wireless access to a network, suchas a transmit receive point (TRP), an enhanced Node B (eNB), amacro-cell, a femtocell, a Wi-Fi access point (AP), or other wirelesslyenabled devices. Base stations may provide wireless access in accordancewith one or more wireless communication protocols, e.g., 5th generationnew radio (5G_NR), long term evolution (LTE), LTE advanced (LTE-A), HighSpeed Packet Access (HSPA), Wi-Fi 802.11a/b/g/n/ac, etc. As used herein,the term “UE” refers to any component (or collection of components)capable of establishing a wireless connection with a base station, suchas a mobile device, a mobile station (STA), and other wirelessly enableddevices. In some embodiments, the network 100 may comprise various otherwireless devices, such as relays, low power nodes, etc.

In some embodiments, motion sensor information generated by one or moremotion sensors of a UE may be used to classify a UE movement. Forexample, motion sensor information may be used to classify the UEmovement as a UE rotation or a UE displacement. Other classificationsare also possible. Classifying the UE movement may be useful in beamrecovery and/or adjustment because different beam management techniquesmay be used for different types of UE movement classifications. By wayof example, a beam blockage, or reduction in QoS, arising from UErotation may generally be addressed by shifting the beam direction ofthe UE in the opposite clockwise or counterclockwise direction as the UErotation (e.g., beam direction is shifted in the counter-clockwisedirection when the UE rotates in the clockwise direction, and viceversa) while maintaining the beam direction of the base station. Asanother example, a beam blockage, or reduction in QoS, arising from UEdisplacement may generally be addressed by adjusting the beam directionof the UE and the beam direction of the base station in the sameclockwise or counter-clockwise directions.

FIGS. 2A-2D are diagrams that show how different beam managementtechniques may be used to adjust beam directions used to transmit andreceive downlink data signals for different classifications of UEmovement. Although the examples described in reference to FIGS. 2A-2Ddescribe beam management in the context of downlink signals, it shouldbe appreciated that the same concepts apply to uplink signals, as wellas other types of beamformed signals, e.g., device to device (D2D)wireless signals, backhaul wireless signals.

FIG. 2A depicts the transmission of an initial downlink signal 233 fromthe base station 210 to the UE 220. The base station 210 uses the beamdirection 213 to transmit the initial downlink signal 233, and the UE220 uses the beam direction 223 to receive the downlink signal.

FIG. 2B depicts a beam blockage condition that occurs duringtransmission of a subsequent downlink signal 234 from the base station210 to the UE 220 after displacement of the UE 220 from an initiallocation to a subsequent location. In this example, the subsequentdownlink signal 234 is transmitted and received using the same beamdirections 213, 223 (respectively) that were used to transmit andreceive the initial downlink signal 233. The beam directions 213, 223 donot provide sufficient antenna gain when the UE 220 is located at thesubsequent location, and as result the UE 220 cannot successfullyreceive/decode the subsequent downlink signal 234.

FIG. 2C depicts a beam adjustment technique that avoids the beamblockage condition following the displacement of the UE 220 from aninitial location to a subsequent location. As shown, when a UEdisplacement movement occurs, beam blockage can be avoided byshifting/adjusting the current beam direction used by the UE in theopposite direction than the current beam direction used by the basestation. In this example, the base station shifts its current beamdirection in the clockwise direction from the beam direction 213 to thebeam direction 214 prior to transmitting the subsequent downlink signal242, and the UE 220 shifts its current beam direction in the clockwisedirection from the beam direction 223 to the beam direction 222 prior toreceiving the subsequent downlink signal 242. The antenna gain providedby the beam directions 214, 222 when the UE 220 is located at thesubsequent location is sufficient to allow the UE 220 to successfullyreceive, and decode, the subsequent downlink signal 242.

FIG. 2D depicts a beam blockage condition that occurs duringtransmission of a subsequent downlink signal 235 after rotation of theUE 220. Similar to FIG. 2B, the subsequent downlink signal 235 istransmitted and received by the base station 210 and the UE 220 usingthe same beam directions 213, 223 (respectively) that were used totransmit and receive the initial downlink signal 233, and thecombination of beam directions 213 and 223 does not provide sufficientantenna gain to allow the UE 220 to successfully receive the subsequentdownlink signal 235 when the UE 220 has its post-rotation orientation.

FIG. 2E depicts a beam adjustment technique that avoids the beamblockage condition following the rotation of the UE 220. As shown, whena UE rotation movement occurs, beam blockage can be avoided by shiftingthe current beam direction of the UE. In this example, the UE 220 shiftsits current beam direction from the beam direction 223 to the beamdirection 222 prior to receiving the subsequent downlink signal 232. Theantenna gain provided by the beam directions 213 and 222 when the UE 220has its post-rotation orientation is sufficient to allow the UE 220 tosuccessfully receive, and decode, the subsequent downlink signal 232.

As can be appreciated by comparing FIG. 2C and FIG. 2E, the beamadjustment techniques for UE rotation and UE displacement movementclassifications are different in so far as UE displacement typicallyrequires that both the UE and the base station adjust their current beamdirections, while UE rotation generally only requires the UE to adjustits current beam direction. Although FIGS. 2C and 2E depict embodimentbeam management techniques between a mobile UE 220 and a stationary basestation 210, it should be appreciated that other embodiment beammanagement techniques may occur between two mobile devices (e.g.,between a mobile UE and a mobile base station, between a mobile UE and amobile relay station, between two mobile UEs, etc.), and that motionsensor information may be generated by motion sensors on both mobiledevices as well as exchanged between the respective mobile devicesand/or a location server.

Using sensor information to detect a UE movement may allow the UE and/orbase station to initiate beam adjustment procedures more quickly than ifthey relied solely on beam-tracking reference signals for severalreasons. For example, motion sensor information may be more responsiveto UE movements due to the propagation delay of the channel.Additionally, the sensor measurements may be used to definitivelyascertain the presence of UE movement, while the reference signalmeasurements may only indicate that the air interface has changed, whichcould be caused by various factors, such as a physical object passingthrough the line-of-sight path between the UE and the base station.

Additionally, the sensor measurements may be updated more frequentlythan the reference signal measurements. For example, the sensormeasurements may be generated almost continuously (e.g., every few clockcycles of the move sensor's processor), while reference signals aretypically transmitted on a periodic basis (e.g., every ten TTIs, etc.)to reduce the amount of overhead required to perform beam-tracking.Additionally, the sensor measurements may detect smaller amounts of UEmovement (e.g., smaller degrees of angular rotation, shorterdisplacement distances) than reference signal measurements depending onthe sensitivity of the movement sensors. For these and other reasons,embodiment techniques may be able to initiate beam direction adjustmentmuch closer to the instant in which the UE rotation or displacementbegins than conventional beam-tracking techniques that rely solely onreference signal measurements.

An additional benefit is that sensor information allows the UE movementto be classified. This may allow the UE and/or base station to select abeam adjustment solution that is tailored to the classification of theUE movement. For example, if the UE movement is classified as arotation, then the beam adjustment technique may adjust the beamdirection of the UE while maintaining the beam direction of the basestation, thereby reducing the time required to perform beam adjustment.Additionally, motion sensor information may allow the UE movement to bequantified, thereby further refining the selection of the adjustmentsolution. For example, motion sensor information may allow the UE todetermine the direction of rotation, as well as to estimate the rateand/or amount of angular rotation, thereby allowing the UE to hone inthe appropriate beam direction adjustment more quickly. For thesereasons, using motion sensor information to aid in beam management mayfurther mitigate beam blockage, as well as reduce the latency associatedwith beam recovery following a beam blockage condition.

In some embodiments, a UE will use GNSS coordinates of base stations inconjunction with motion sensor information for beam management as wellas to determine when a handover is appropriate. FIG. 3 is a diagram ofan embodiment network 300 in which GNSS coordinates of base stations maybe used for beam management and/or to initiate a handover. In oneexample, the UE 320 may use GNSS coordinates of the serving base station310 in conjunction with motion sensor information generated by motionsensors of the UE 320 to determine a beam direction adjustment for theUE 320 and/or a beam direction adjustment recommendation for the basestation 310. In another example, the UE 320 uses GNSS coordinates of theserving base station 310 and/or the neighboring base stations 312, 314in conjunction with motion sensor information generated by motionsensors of the UE 320 to initiate a handover. In some embodiments, theUE 320 may request GNSS coordinates of a subset of neighboring basestations, and the serving base station 310 may provide the GNSScoordinates of neighboring base stations in the subset specified by theUE 320 without providing GNSS coordinates of neighboring base stationsexcluded from the subset specified by the UE 320. In yet otherembodiments, the location server 390 may receive motion information fromthe UE 320, and process it to determine beam direction adjustmentsand/or to initiate handovers.

FIG. 4 is a diagram of an embodiment UE 400 configured to perform beammanagement based on sensor information of movement sensors 410 of the UE400. The movement sensors 410 may include an accelerometer 412, agyroscope 414, a magnetometer 416, and a GNSS sensor 418. Theaccelerometer 412 may include any component or collection of componentsthat measures physical acceleration experienced by the UE 400. Thegyroscope 414 may include any component or collection of components thatmeasures an orientation of the UE 400. The magnetometer 416 may includeany component or collection of components that measures the orientationof the UE 400 relative to the earth, e.g., similar to the way a compassgauges direction. The GNSS sensor 418 may include any component orcollection of components that gauges a geo-spatial positioning of the UE400 based at least in part on signals received from a GNSS.

The UE 400 further includes a movement classifier 420. The movementclassifier uses sensor information generated by the movement sensors410, in conjunction with training data 430 reference signal measurements440, to classify a movement of the UE 400. The UE movementclassification is then provided to the beam management controller 450,where it is used to select one or more of a static movementconfiguration 442, a rotation configuration 444, a displacementconfiguration 446, and a beam blockage configuration 448. The staticmovement configuration 442 may specify one or more beam managementtechniques that may be implemented when the UE 400 is static, or ismoving/rotating at relatively low rates of speed. The rotationconfiguration 444 may specify one or more beam management techniquesthat may be implemented when the UE 400 is rotating at an angularvelocity that exceeds a threshold. The displacement configuration 446may specify one or more beam management techniques that may beimplemented when the UE 400 is moving at speed that exceeds a threshold.The beam blockage configuration 448 may specify one or more beamrecovery techniques that may be implemented after the UE 400 hasexperienced a beam blockage condition.

FIG. 5 is a flowchart of a method 500 for using motion sensorinformation to update TX/RX parameters of a base station, as may beperformed by a UE. At step 510, the UE transmits or receives an initialsignal to or from a base station. At step 520, the UE collects sensorinformation from one or more motion sensors of the UE. At step 530, theUE determines a TX/RX parameter adjustment for the base station based onmotion sensor information. In an embodiment, the UE determines the TX/RXparameter adjustment by classifying a movement of the UE based on themotion sensor information, and determining the TX/RX parameteradjustment recommendation based on the classification of the UEmovement. The UE may classify the UE movement directly without externalassistance. At step 540, the UE sends a UE-initiated recommendation tothe base station recommending that the base station perform the TX/RXparameter adjustment prior to transmitting or receiving a subsequentsignal from to or from the UE.

The UE-initiated recommendation may recommend that the base stationadjust a beam direction used to transmit or receive the initial signalprior to transmitting or receiving the subsequent signal by, forexample, including a new beam index, a new beam pair index, and/or a newresource index. Alternatively, the UE-initiated recommendation mayrecommend that the base station adjust a TX/RX scheme used to transmitor receive the initial signal prior to transmitting or receiving thesubsequent signal. The UE-initiated recommendation may be transmittedover the same frequency as the initial and/or subsequent signal.Alternatively, the UE-initiated recommendation may be transmitted over alower carrier frequency, or a higher carrier frequency, than the initialand/or subsequent signal. For instance, the UE-initiated recommendationcould be sent over a 4G LTE carrier frequency (e.g., between 0.4 GHz and6 GHz), and the initial and/or subsequent signal could be transmittedover a mmWave carrier frequency (e.g., above 6 GHz). The UE-initiatedrecommendation may be transmitted over grant-free resources of a randomaccess channel to reduce latency associated with a grant request.Alternatively, the UE-initiated recommendation may be transmitted overpersistently or semi-persistently scheduled resources. In an embodiment,the UE-initiated recommendation is a media access control (MAC) CEcommand, or physical (PHY) layer control signal.

FIG. 6 is a flowchart of a method 600 for using motion sensorinformation to update a beam direction of a UE. At step 610, the UEtransmits or receives an initial signal to or from a serving basestation in accordance with a beam direction. At step 620, the UEcollects sensor information from one or more motion sensors of the UE.At step 630, the UE adjusts the beam direction used to transmit orreceive the initial signal. At step 640, the UE transmits or receives asubsequent signal over the antenna of the UE in accordance with theadjusted beam direction.

FIG. 7 is a flowchart of a method 700 for using GNSS coordinates ofneighboring base stations to initiate a handover of a UE from a servingbase station to a target base station. At step 710, the UE transmits orreceives an initial signal to or from a serving base station. At step720, the UE receives GNSS coordinates of one or more neighboring basestations of the serving base station. At step 730, the UE identifies,based on a movement of the UE, one or more of the neighboring basestations as target base stations according to the GNSS coordinates. Atstep 740, the UE sends a handover recommendation to the serving basestation or at least one of the target base stations. The handoverrecommendation recommends a handover of the UE from the serving basestation to one of the target base stations.

FIG. 8 is a flowchart of a method 800 for using motion information of aUE to determine a TX/RX parameter adjustment recommendation for aserving base station or the UE, as may be performed by a locationserver. At step 810, the location server receives sensor informationfrom one or motion sensors of the UE. At step 820, the location serverdetermines a TX/RX parameter adjustment recommendation for the servingbase station or the UE based on motion sensor information of the UE. Atstep 830, the UE sends the TX/RX parameter adjustment recommendation tothe UE or to the serving base station.

FIG. 9 is a protocol diagram of a communications sequence for using alocation server to provide beam-tracking assistance. As shown, the UEand the location server exchanging signaling 910 to set up a mobileoriginating positioning session via an MME. Next, the UE receivesreference signals 920 from one or more base stations, and determinessensor measurements and GNSS measurements, which are then provided tothe location server for position computation. The location server thenreturns a position estimate 940 that includes angular information to theUE. The UE then determines beam IDs based on the angular information,and sends a signal 950 that includes information relating to beamtracking/selection to at least one of the one or more base stations.

As mentioned above, the movement of a device may lead to a degradationin signal quality. Table 1 illustrates typical angular displacements ofa device for several common activities.

TABLE 1 Angular displacement Activity in 100 ms (degrees) Reading, webbrowsing  6-11 Horizontal to vertical changes 30-36 Playing games 72-80

In some embodiments, motion sensors of a UE detect a UE-initiated beamfailure event and/or trigger a UE-initiated beam recovery procedure. Inother embodiments, reference signals are communicated over channelsassociated with different beam direction in order to detect aUE-initiated beam failure event and/or trigger a UE-initiated beamrecovery procedure.

In some embodiments, a UE transmits uplink reference signals over uplinkchannels associated with different uplink transmit and/or receive beamdirections, and waits to see if the base station returns anacknowledgement message associated with any of the uplink referencesignals. If no acknowledgement message is received prior to expirationof a time-out period, then the UE detect a UE-initiated beam failureevent, and send a signal to the base station indicating that theUE-initiated beam failure event has occurred. As mentioned above, a UEmay send a signal indicating that the UE-initiated beam failure eventhas occurred. The signal indicating that the UE-initiated beam failureevent has occurred may be communicated over grant-free resources, suchas a physical random access channel (PRACH) used for initial access or arandom access channel that spans different time and/or frequencyresources than the PRACH channel. Alternatively, the signal indicatingthat the UE-initiated beam failure event has occurred may becommunicated over a physical uplink control channel (PUCCH) or aphysical uplink shared channel (PUSCH).

As mentioned above, at least some of the uplink channels are associatedwith different transmit or receive beam directions. In one example, theuplink channels are physical uplink control channels (PUCCH₁, PUCCH₂, .. . , PUCCH_(N)), and each PUCCH is associated with an uplink transmitbeam v_(ti) and/or an uplink receive beam v_(ri), where t indicates atransmit beam, r indicates a receive beam, and i is the index of theuplink channel. For each eNB and UE pair, the UE determines which uplinktransmit beam v_(ri) to associate with a given PUCCH, and the eNBdetermines which uplink receive beam v_(ri) to associate with a givenPUCCH. The UE may transmit a signal (e.g., a reference signal, acommand, etc.) over all or some of the PUCCHs using the correspondinguplink transmit beam v_(ti), and the eNB may attempt to detect thesignals over all or some of the PUCCHs using the corresponding uplinkreceive beam v_(ri). When the eNB detects a signal over a particularuplink control channel (e.g., PUCCH_(i)), the eNB sends a positiveconfirmation command/message to the UE indicating that the correspondingsignal was received. If no signal is detected for a particular channel,then the eNB does not send a corresponding positive confirmation to theUE. If upon expiration of a timeout period, the UE has not received anypositive confirmation commands from the eNB, then the UE detects that abeam failure event has occurred and/or triggers a beam recoveryprocedure.

FIG. 10 is a protocol diagram of an embodiment communications sequence1000 for detecting a beam failure event based on uplink referencesignals 1010. As shown, the UE transmits the uplink reference signals1010 over different PUCCHs in a set of PUCCHs. In some embodiments, theUE uses different uplink transmit beams to transmit the uplink referencesignals 1010 over at least some of the PUCCHs, and the eNB usesdifferent uplink receive beams when attempting to detect the uplinkreference signals 1010 over at least some of the PUCCHs. In this way,different combinations of TX and RX uplink beams can be evaluatedthrough communication of the uplink reference signals 1010. If the eNBsuccessfully detects one or more of the signals 1010, then the eNB sendsone or more confirmation messages 1020 to the UE confirming that thesignal was correctly received. In one example, the confirmation messages1020 include an index associated with the corresponding PUCCH. Inanother example, the confirmation messages 1020 are transmitted overresources (e.g., PDCCHs, etc.) that are associated with thecorresponding PUCCHs, thereby allowing the UE to implicitly determinewhich PUCCH message was successfully received by the eNB. At step 1030,the UE determines whether at least one confirmation message was receivedfrom the base station prior to expiration of a timeout period. If so,then the UE performs a data transmission, or otherwise receives datatransmission, using a given one of the beam directions. If noconfirmation message was received from the base station prior toexpiration of the timeout period, then the UE detects a beam failureevent at step 1050, and triggers, or otherwise initiates, a beamrecovery procedure at step 1060.

Although the uplink reference signals 1010 are depicted as beingtransmitted over PUCCHs, it should be appreciated that other types ofuplink channels may be used in place of, or in conjunction with, thePUCCHs. For example, the uplink reference signals 1010 could becommunicated over PUSCHs. As another example, the uplink referencesignals 1010 could be transmitted over uplink grant-free channels. Insuch an example, the uplink reference signals low may be transmittedover a physical random access channel (PRACH) used for initial access.Alternatively, the uplink reference signals 1010 may be transmitted overa random access channel that spans different time and/or frequencyresources than a physical random access channel (PRACH) used for initialaccess.

Downlink channels can also be used for communicating reference signalsused to detect a UE-initiated beam failure event and/or trigger aUE-initiated beam recovery procedure. In an example, each of a pluralityof physical downlink control channels (PDCCH₁, PDCCH₂, . . . PUCCH_(N))is associated with a downlink transmit beam w_(ti) and/or an uplinkreceive beam w_(ri), where t indicates a transmit beam, r indicates areceive beam, and i is the index of the downlink channel. For each eNBand UE pair, the UE determines which downlink receive beam w_(ri) toassociate with a given PDCCH, and the eNB determines which downlinktransmit beam w_(ti) to associate with a given PDCCH. The eNB maytransmit a signal (e.g., a reference signal, a command, etc.) over allor some of the PDCCHs using the corresponding downlink transmit beamw_(ti), and the UE may attempt to receive the signals over all or someof the PDCCHs using the corresponding downlink receive beam w_(ri). Ifupon expiration of a time period, the UE has not detected a signal overany of the PDCCHs, then the UE may determine that a beam failure eventhas occurred and/or trigger a beam recovery procedure. It should beappreciated that downlink data channels (e.g., PDSCHs, etc.) may be usedin place of, or in conjunction with, the PDCCHs for communicating thesignals used to detect the beam failure event.

FIG. 11 is a protocol diagram of an embodiment communications sequence1100 for detecting a beam failure event based on downlink signals 1110.As shown, the base station transmits the downlink signals 1110 overdifferent PDCCHs in a set of PDCCHs. Different downlink transmit beamsmay be used to transmit the downlink signals 1110 over at least some ofthe PDCCHs and/or different downlink receive beams may be used toreceive, or otherwise attempt to detect, the downlink signals 1110 overat least some of the PDCCHs. In this way, different combinations of TXand RX downlink beams can be evaluated through communication of thedownlink signals 1110. At step 1130, the UE determines whether at leastone of the downlink reference signals 1110 were successfullyreceived/detected prior to expiration of a timeout period. If so, thenthe UE performs a data transmission, or otherwise receives datatransmission, using a given one of the beam directions. If noconfirmation message was received from the base station prior toexpiration of the timeout period, then the UE detects a beam failureevent at step 1150, and triggers, or otherwise initiates, a beamrecovery procedure at step 1160.

A base station may assign a unique signal parameter, or resource, toeach UE, and the UE may transmit in accordance with the assignedparameter, or over the assigned resource, in order to request, orotherwise trigger/initiate, a beam recovery procedure. The base stationmay assign the unique signal-parameter/resource during, or immediatelyafter, a link establishment procedure, during which time the UEestablishes an active link with the base station. In one embodiment, theassigned signal-parameter/resource is a UE-specific preamble sequencethat is used to transmit a signal over a random access channel/region,e.g., a RACH region, etc. In such an embodiment, UEs may transmitsignals carrying their assigned UE-specific preamble sequences over therandom access channel in order to request, or otherwisetrigger/initiate, a beam recovery procedure, and the base station mayidentify which UE transmitted a given signal over the RACH based on theUE-specific preamble sequence carried by the signal. In anotherembodiment, the assigned signal-parameter/resource is a UE-specificresource element (RE), or a UE-specific set of REs, in a control channelor control region of a subframe. In such an embodiment, UEs may transmitsignals over their respective UE-specific REs in order to request, orotherwise trigger/initiate, a beam recovery procedure, and the basestation may identify which UE transmitted a given one of the signalbased on the RE(s) over which the signal was received.

In some other embodiments, a UE may determine when to request, orotherwise trigger/initiate, a beam recovery procedure by monitoring oneor more downlink channels, such as physical downlink control channels(PDCCHs) and/or physical downlink shared channels (PDSCHs). PDCCHs maybe used to carry downlink control messages. PDSCHs may be used to carrydownlink control messages as well as downlink data transmissions. Asignal for requesting, or otherwise triggering/initiating, a beamrecovery procedure may be transmitted over one or more uplink channels,such as physical uplink control channels (PUCCHs) and/or physical uplinkshared channels (PUSCHs). PUCCHs may be used to carry uplink controlmessages. PUSCHs may be used to carry uplink control messages as well asuplink data.

In one embodiment, UE may monitor one or more downlink channels for atimeout period. If no downlink signals are detected prior to expirationof the timeout period, then the UE may request, or otherwisetrigger/initiate, a beam recovery procedure. In general, the UE maydetect a downlink signal when a received signal power or quality levelof a monitored channel exceeds a predetermined threshold.

In another embodiment, a UE may send signals (e.g., commands, controlmessages, reference signals, etc.) over one or more uplink channels, andthen monitor one or more downlink channels for acknowledgementindications associated with the uplink signals. If no acknowledgementindications are received prior to expiration of a timeout period, thenthe UE may request, or otherwise trigger/initiate, a beam recoveryprocedure.

A UE may request, or otherwise trigger/initiate, a beam recoveryprocedure by transmitting a signal over an uplink channel. The signalmay carry, or otherwise be associated with, a signal parameter that hasbeen assigned to the UE. Alternatively, the signal may be transmittedover a resource assigned to the UE. The assigned signal parameter and/orresource may be used by the base station to determine which UE isrequesting, or otherwise triggering/initiating, a beam recover procedureupon reception of the corresponding signal.

The channel over which the uplink signal that requests, or otherwisetriggers/initiates, the beam recovery event may be different than othercontrol or data channels that are used to transmit other types of UEreports, such as channel quality indicator (CQIs), acknowledgement(ACKs), and/or channel information feedback. The channel may be agrant-based access channel or a grant-free access channel. In order totransmit a signal over a grant-based access channel, a UE is generallyrequired to request, and thereafter obtain, a resource grant.Conversely, a UE may generally be permitted transmit a signal over agrant-free access channel without first obtaining/requesting a resourcegrant. Various access control mechanisms, such as carrier-sense multipleaccess with collision avoidance (CSMA/CA), may be used to mitigatecollisions between transmissions of different UEs over grant-free accesschannels.

In conventional 4G LTE networks, a UE that is in an idle state maytransmit an initial access request over an Initial Access Random AccessChannel (IA-RACH) in order to request that PUSCH resources be scheduledfor an uplink data transmissions of the UE. However, in conventional 4GLTE networks, UEs that are in the connected state are generally notpermitted to transmit signals over random access channels. Inembodiments of this disclosure, a UE that is operating in the connectedstate may transmit a preamble sequence over a random access channel, inorder to request, or otherwise trigger/initiate, a beam recovery event.In one example, the preamble sequence is transmitted over a randomaccess channel that is different than the IA-RACH. In such an example,the random access channel over which the preamble sequence istransmitted over may be associated with a different carrier frequencythan the IA-RACH.

FIG. 12 illustrates a block diagram of an embodiment processing system1200 for performing methods described herein, which may be installed ina host device. As shown, the processing system 1200 includes a processor1204, a memory 1206, and interfaces 1210-1214, which may (or may not) bearranged as shown in FIG. 12. The processor 1204 may be any component orcollection of components adapted to perform computations and/or otherprocessing related tasks, and the memory 1206 may be any component orcollection of components adapted to store programming and/orinstructions for execution by the processor 1204. A means forconfiguring a context for a UE may include processor 1204. In anembodiment, the memory 1206 includes a non-transitory computer readablestorage medium that stores programming for execution by the processor1204. The interfaces 1210, 1212, 1214 may be any component or collectionof components that allow the processing system 1200 to communicate withother devices/components and/or a user. For example, one or more of theinterfaces 1210, 1212, 1214 may be adapted to communicate data, control,or management messages from the processor 1204 to applications installedon the host device and/or a remote device. As another example, one ormore of the interfaces 1210, 1212, 1214 may be adapted to allow a useror user device (e.g., personal computer (PC), etc.) tointeract/communicate with the processing system 1200. The processingsystem 1200 may include additional components not depicted in FIG. 12,such as long term storage (e.g., non-volatile memory, etc.).

In some embodiments, the processing system 1200 is included in a networkdevice that is accessing, or part otherwise of, a telecommunicationsnetwork. In one example, the processing system 1200 is in a network-sidedevice in a wireless or wireline telecommunications network, such as anetwork TRP, a relay station, a scheduler, a controller, a gateway, arouter, an applications server, or any other device in thetelecommunications network. In other embodiments, the processing system1200 is in a user-side device accessing a wireless or wirelinetelecommunications network, such as a mobile station, a user equipment(UE), a personal computer (PC), a tablet, a wearable communicationsdevice (e.g., a smartwatch, etc.), or any other device adapted to accessa telecommunications network.

In some embodiments, one or more of the interfaces 1210, 1212, 1214connects the processing system 1200 to a transceiver adapted to transmitand receive signaling over the telecommunications network. FIG. 13illustrates a block diagram of a transceiver 1300 adapted to transmitand receive signaling over a telecommunications network. The transceiver1300 may be installed in a host device. As shown, the transceiver 1300comprises a network-side interface 1302, a coupler 1304, a transmitter1306, a receiver 1308, a signal processor 1310, and a device-sideinterface 1312. The network-side interface 1302 may include anycomponent or collection of components adapted to transmit or receivesignaling over a wireless or wireline telecommunications network. Thenetwork-side interface 1302 may also include any component or collectionof components adapted to transmit or receive signaling over ashort-range interface. The network-side interface 1302 may also includeany component or collection of components adapted to transmit or receivesignaling over a Uu interface. The coupler 1304 may include anycomponent or collection of components adapted to facilitatebi-directional communication over the network-side interface 1302. Thetransmitter 1306 may include any component or collection of components(e.g., up-converter, power amplifier, etc.) adapted to convert abaseband signal into a modulated carrier signal suitable fortransmission over the network-side interface 1302. A means fortransmitting an initial message of an access procedure may includetransmitter 1306. The receiver 1308 may include any component orcollection of components (e.g., down-converter, low noise amplifier,etc.) adapted to convert a carrier signal received over the network-sideinterface 1302 into a baseband signal. A means for receiving mobilesubscriber identifiers, initial downlink messages of access procedures,and forwarded requests to connect to a network may include receiver1308.

The signal processor 1310 may include any component or collection ofcomponents adapted to convert a baseband signal into a data signalsuitable for communication over the device-side interface(s) 1312, orvice-versa. The device-side interface(s) 1312 may include any componentor collection of components adapted to communicate data-signals betweenthe signal processor 1310 and components within the host device (e.g.,the processing system 1200, local area network (LAN) ports, etc.).

The transceiver 1300 may transmit and receive signaling over any type ofcommunications medium. In some embodiments, the transceiver 1300transmits and receives signaling over a wireless medium. For example,the transceiver 1300 may be a wireless transceiver adapted tocommunicate in accordance with a wireless telecommunications protocol,such as a cellular protocol (e.g., long-term evolution (LTE), etc.), awireless local area network (WLAN) protocol (e.g., Wi-Fi, etc.), or anyother type of wireless protocol (e.g., Bluetooth, near fieldcommunication (NFC), etc.). In such embodiments, the network-sideinterface 1302 comprises one or more antenna/radiating elements. Forexample, the network-side interface 1302 may include a single antenna,multiple separate antennas, or a multi-antenna array configured formulti-layer communication, e.g., single input multiple output (SIMO),multiple input single output (MISO), multiple input multiple output(MIMO), etc. In other embodiments, the transceiver 1300 transmits andreceives signaling over a wireline medium, e.g., twisted-pair cable,coaxial cable, optical fiber, etc. Specific processing systems and/ortransceivers may utilize all of the components shown, or only a subsetof the components, and levels of integration may vary from device todevice.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments, as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is therefore intended that the appended claims encompassany such modifications or embodiments.

1. A method comprising: receiving, by a user equipment (UE), one or moredownlink reference signals from a first base station over a firstcarrier frequency; detecting, by the UE, a beam failure event associatedwith one or more beams based on measurement of the one or more downlinkreference signals; and based thereon transmitting, by the UE, a physicalrandom access channel (PRACH) transmission to initiate beam failurerecovery responsive to the beam failure event.
 2. The method of claim 1,wherein the PRACH transmission indicates a recommendation for a new beamdirection for the first base station to use for data transmissions tothe UE.
 3. The method of claim 1, wherein the PRACH transmissionindicates a recommendation to initiate a beam management procedure. 4.The method of claim 1, wherein transmitting the PRACH transmission toinitiate the beam failure recovery responsive to the beam failure eventincludes transmitting the PRACH transmission over a PRACH resourceelement (RE) that is uniquely associated with, or otherwise assigned to,the beam failure event or a beam failure recovery procedure.
 5. Themethod of claim 4, wherein the PRACH RE is a UE-specific RE.
 6. Themethod of claim 1, wherein transmitting the PRACH transmission toinitiate the beam failure recovery responsive to the beam failure eventincludes transmitting the PRACH transmission using a preamble that isuniquely associated with, or otherwise assigned to, the beam failureevent or a beam failure recovery procedure.
 7. The method of claim 6,wherein the preamble is a UE-specific preamble.
 8. The method of claim1, wherein the PRACH transmission is received over a second carrierfrequency that is different than the first carrier frequency.
 9. Themethod of claim 1, wherein the PRACH transmission is transmitted to thefirst base station.
 10. The method of claim 1, wherein the PRACHtransmission is transmitted to a second base station that is differentthan the first base station.
 11. An user equipment (UE) comprising: aprocessor; and a non-transitory computer readable storage medium storingprogramming for execution by the processor, the programming includinginstructions to: receive one or more downlink reference signals from afirst base station over a first carrier frequency; detect a beam failureevent associated with one or more beams based on measurement of the oneor more downlink reference signals; and based thereon to transmit aphysical random access channel (PRACH) transmission to initiate beamfailure recovery responsive to the beam failure event.
 12. The UE ofclaim 11, wherein the PRACH transmission indicates a recommendation fora new beam direction for the first base station to use for datatransmissions to the UE.
 13. The UE of claim 11, wherein the PRACHtransmission indicates a recommendation to initiate a beam managementprocedure.
 14. The UE of claim 11, wherein the instructions to transmitthe PRACH transmission to initiate the beam failure recovery responsiveto the beam failure event include instructions to transmit the PRACHtransmission over a PRACH resource element (RE) that is uniquelyassociated with, or otherwise assigned to, the beam failure event or abeam failure recovery procedure.
 15. The UE of claim 14, wherein thePRACH RE is a UE-specific RE.
 16. The UE of claim 11, wherein theinstructions to transmit the PRACH transmission to initiate the beamfailure recovery responsive to the beam failure event includeinstructions to transmit the PRACH transmission using a preamble that isuniquely associated with, or otherwise assigned to, the beam failureevent or a beam failure recovery procedure.
 17. The UE of claim 16,wherein the preamble is a UE-specific preamble.
 18. The UE of claim 11,wherein the PRACH transmission is transmitted over a second carrierfrequency that is different than the first carrier frequency.
 19. The UEof claim 11, wherein the PRACH transmission is transmitted to the firstbase station.
 20. The UE of claim 11, wherein the PRACH transmission istransmitted over a second carrier frequency that is different than thefirst carrier frequency.
 21. A method comprising: transmitting, by abase station, one or more downlink reference signals to a user equipment(UE) over a first carrier frequency using a first beam direction;receiving and decoding, by the base station, a physical random accesschannel (PRACH) transmission of the UE; and based thereon initiating, bythe base station, a beam failure recovery procedure responsive to a beamfailure event for the first beam direction indicated by the PRACHtransmission of the UE, the beam failure event for the first beamdirection detected by the UE based on measurements of the one or moredownlink reference signals.
 22. The method of claim 21, wherein thePRACH transmission is received over a PRACH resource element (RE) thatis uniquely associated with, or otherwise assigned to, the beam failureevent or a beam failure recovery procedure.
 23. The method of claim 22,wherein the PRACH RE is a UE-specific RE.
 24. The method of claim 21,wherein decoding the PRACH transmission comprises identifying a preambleused to transmit the PRACH transmission, the preamble being uniquelyassociated with, or otherwise assigned to, the beam failure event or abeam failure recovery procedure.
 25. The method of claim 24, wherein thepreamble is a UE-specific preamble.
 26. The method of claim 21, whereinthe PRACH transmission is received over a second carrier frequency thatis different than the first carrier frequency.
 27. A base stationcomprising: a processor; and a non-transitory computer readable storagemedium storing programming for execution by the processor, theprogramming including instructions to: transmit one or more downlinkreference signals to a user equipment (UE) over a first carrierfrequency using a first beam direction; receive and decode a physicalrandom access channel (PRACH) transmission of the UE; and based thereoninitiate a beam failure recovery procedure responsive to a beam failureevent for the first beam direction and indicated by the PRACHtransmission of the UE, the beam failure event for the first beamdirection detected by the UE based on measurements of the one or moredownlink reference signals.
 28. The base station of claim 27, whereinthe PRACH transmission is received over a PRACH resource element (RE)that is uniquely associated with, or otherwise assigned to, the beamfailure event or a beam failure recovery procedure.
 29. The base stationof claim 28, wherein the PRACH RE is a UE-specific RE.
 30. The basestation of claim 27, wherein the instructions to decode the PRACHtransmission include instructions to identify a preamble used totransmit the PRACH transmission, the preamble being uniquely associatedwith, or otherwise assigned to, the beam failure event or a beam failurerecovery procedure.
 31. The base station of claim 30, wherein thepreamble is a UE-specific preamble.
 32. The base station of claim 27,wherein the PRACH transmission is received over a second carrierfrequency that is different than the first carrier frequency.